PCT Patent Publications WO 04/067528 and WO 06/062978 disclose methods for the preparation of 3-bromo-1-(3-chloro-2-pyridinyl)-N-[4-cyano-2-methyl-6-[(methylamino)-carbonyl]phenyl]-1H-pyrazole-5-carboxamide (Compound 1), as well as the utility of this compound as an insecticide. WO 06/062978 further discloses the purification of Compound 1 by recrystallization from 1-propanol.
It is well known in the art that certain crystalline compounds can exist as polymorphs. The term “polymorph” refers to a particular crystalline form of a chemical compound that can crystallize in different crystalline forms, these forms having different arrangements and/or conformations of the molecules in the crystal lattice. Although polymorphs can have the same chemical composition, they can also differ in composition due the presence or absence of co-crystallized water or other molecules, which can be weakly or strongly bound in the lattice. Polymorphs can differ in such chemical, physical and biological properties as crystal shape, density, hardness, color, chemical stability, melting point, hygroscopicity, suspensibility, dissolution rate and biological availability.
Thus far, it has not been possible to predict the occurrence and number of crystalline polymorphs of any single compound, nor the particular physicochemical properties of any particular polymorph. Most importantly, thermodynamic stability and potentially different behavior after administration in living organisms cannot be determined in advance.